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The Lancet, <http://www.thelancet.com/journals/lancet/issue/vol368no9548/PIIS0140-6736(06)X6219-0>Volume 368, Issue 9548, Pages 1706 - 1728, 11 November 2006

Sexual behaviour in context: a global perspective

rof Kaye Wellings FRCOG a
Corresponding Author
<mailto:kaye.wellings@lshtm.ac.uk>
Email Address
, Martine Collumbien MSc a, Emma Slaymaker MSc a, Susheela Singh PhD b, Zoé Hodges MSc a, Dhaval Patel PhD c, Nathalie Bajos PhD d



Summary

Research aimed at investigating sexual behaviour and assessing interventions to improve sexual health has increased in recent decades. The resulting data, despite regional differences in quantity and quality, provide a historically unique opportunity to describe patterns of sexual behaviour and their implications for attempts to protect sexual health at the beginning of the 21st century. In this paper we present original analyses of sexual behaviour data from 59 countries for which they were available. The data show substantial diversity in sexual behaviour by region and sex. No universal trend towards earlier sexual intercourse has occurred, but the shift towards later marriage in most countries has led to an increase in premarital sex, the prevalence of which is generally higher in developed countries than in developing countries, and is higher in men than in women. Monogamy is the dominant pattern everywhere, but having had two or more sexual partners in the past year is more common in men than in women, and reported rates are higher in industrialised than in non-industrialised countries. Condom use has increased in prevalence almost everywhere, but rates remain low in many developing countries.
The huge regional variation indicates mainly social and economic determinants of sexual behaviour, which have implications for intervention. Although individual behaviour change is central to improving sexual health, efforts are also needed to address the broader determinants of sexual behaviour, particularly those that relate to the social context. The evidence from behavioural interventions is that no general approach to sexual-health promotion will work everywhere and no single-component intervention will work anywhere. Comprehensive behavioural interventions are needed that take account of the social context in mounting individual-level programmes, attempt to modify social norms to support uptake and maintenance of behaviour change, and tackle the structural factors that contribute to risky sexual behaviour.
This is the second in a Series of six articles about sexual and reproductive health
The ability of individuals or couples to pursue a fulfilling and safe sex life is central to achievement of sexual health. Creation of supportive environments in which safe sexual behaviour can take place is vital if the Millennium Development Goals (MDGs) for sexual equality, maternal health, and HIV/AIDS are to be achieved.1 Conventionally, public health has focused on adverse outcomes of sexual behaviour. As important determinants of fertility patterns and transmission of sexually transmitted infections, sexual behaviours contribute substantially to the burden of disease.2—4 The past decade has seen growing attention in the international policy arena to sexual rights, and new standards are being formulated for the creation and maintenance of a sexually healthy society, invoking values of dignity, respect, and choice.5 Information about sexual behaviour is essential to the design and assessment of interventions to improve sexual health. Importantly, too, empirical evidence is needed to correct myths in public perception of behaviours. Yet despite being scrutinised everywhere, sexual behaviour poses challenges for scientific enquiry. The same paradox is seen in relation to intervention; sexual activity is strongly regulated in virtually every society, but its modification to improve sexual health has proved difficult.
The need to predict and prevent transmission of HIV has provided a valuable impetus to both sexual behaviour and intervention studies in the past two decades.6, 7 Data are sparser in some regions than others, in particular those with low HIV prevalence or strong prohibitions surrounding sex, or both. African countries, for example, have received hugely disproportionate attention from researchers compared with Asian countries, and so the evidence base is partial. Even so, a reasonable global impression can be gained from the large number of developing countries with comparable data (those for which a Demographic and Health Survey (DHS) has been undertaken8), and from other countries with comparable national surveys. Data are accumulating too, from assessments of the effect of interventions to improve sexual health.
The resulting evidence provides a historically unique opportunity to take stock of sexual behaviour and efforts to protect sexual health at the beginning of the 21st century. Sexual behaviour changes in response to both secular and non-secular social forces. Recent decades have seen large socioeconomic changes in poverty, education, and employment. Demographic changes have taken place, in the age structure of populations, in the timing of marriage, and in the scale of mobility and migration between and within countries, including seasonal labour, rural-to-urban movement, and social disruption due to war and political instabilities. Attitudes to sexual behaviour have altered in many countries.9, 10 Worldwide communications, including the internet,11 have had a bearing on social norms, transporting sexual images from more liberal to more conservative societies, especially those in which advances in information technology have been rapid.12 Advances in contraception have increasingly freed sexual expression from its reproductive consequences. Policy and legislation that govern health-care systems and public-health strategies have also wrought changes;13 access to family-planning services has increased, and few areas have been unaffected by efforts to prevent HIV transmission. We describe current trends and patterns in important variables of sexual behaviour, and their implications for sexual-health status and the design of sexual-health interventions. We present our key messages in panel 1.
Panel 1
Key messages
  * Information about sexual behaviour is essential to inform preventive strategies and to correct myths in public perceptions of sexual behaviour. Increased research in this area in the past two decades provides a historically unique opportunity to take stock of sexual behaviour, and efforts to safeguard it, at the beginning of the 21st century. Gaps in knowledge remain, especially in Asia and the middle east, where obstacles to sexual-behaviour research remain.
  * Trends towards earlier sexual experience are less pronounced and less widespread than sometimes supposed (in many developing countries the trend is towards later onset of sexual activity for women), but the trend towards later marriage has led to an increase in the prevalence of premarital sex.
  * Most people are married and married people have the most sex. Sexual activity in young single people tends to be sporadic, but is greater in industrialised countries than in developing countries.
  * Monogamy is the dominant pattern in most regions; but reporting of multiple partnerships is more common in men than in women, and generally more common in developed countries than in developing countries.
  * Striking differences between men and women in sexual activity are explained in part by a tendency for men to over-report and women to under-report, but patterns of age mixing and the age structures of populations also help explain the difference, especially in African countries.
  * Marriage does not reliably safeguard sexual-health status. Married women find negotiation of safer sex and use of condoms for family planning more difficult than do single women. Very early sexual experience within marriage can be coercive and traumatic.
  * Condom use is increasing—in some ccases, such as in Uganda, strikingly so—but in many developinng countries, rates of use remain low.
  * Factors that determine variations and trends in sexual behaviour are environmental and include shifts in poverty, education, and employment; demographic trends such as the changing age structure of populations and the trend towards later marriage; increased migration between and within countries; globalisation of mass media; advances in contraception and access to family-planning services; and public-health HIV and sexually transmitted disease prevention strategies.
  * Public-health interventions should address the broader determinants of sexual behaviour, such as gender, poverty, and mobility, in addition to individual behaviour change.
  * Risk-reduction messages should respect diversity and preserve choice. Selective emphasis on different aspects of the ABC strategy needs to be tailored to individuals and settings. Young people need to be helped to achieve the best timing of first sex, but first sexual experiences are often forced, or even sold.
  * School-based sex education improves awareness of risk and knowledge of risk reduction strategies, increases self-effectiveness and intention to practice safer sex, and delays rather than hastens the onset of sexual activity.
  * No general approach to sexual-health promotion will work everywhere, and no single-component intervention will work anywhere. We need to know not only whether interventions work, but why and how they do so in particular social contexts. Comprehensive behavioural interventions are needed that take account of the social context, attempt to modify social norms to support uptake and maintenance of behaviour change, and tackle the structural factors that contribute to risky sexual behaviour.


Cross-national comparisons

We compare data for entire countries (panel 2 and table 1) and in so doing we pay less attention to the substantial variability within countries. Our choice of indicators shows a concern with sexual health and human rights, but is also determined by availability of comparable data. Age at sexual initiation is of public health interest, since early initiation is more likely to be non-consensual and to be subsequently regretted,31—33 less likely to be protected against unplanned pregnancy and infection, and associated with larger lifetime numbers of sexual partners.34—36 Risk behaviours for sexuallyy transmitted infections, such as multiple partnerships and sex between men are included as are prevalence estimates of transactional sex, since clients of sex workers are important bridging groups in the transmission of sexually transmitted infections and HIV to wider sexual networks. We include condom use as a marker of safer sex.
Panel 2
Methods
Search strategy
We reviewed medical, public health, and social science research by searching Embase, MEDLINE, Popline, PubMed, and Web of Science electronic databases for articles published between 1996 and 2006 using the key words “sexual behaviour† and “sexual behaviour change†. We also contacted experts in sexual behaviour studies, we hand-searched AIDS, The Lancet, and Social Science and Medicine, we found references cited by key papers, and accessed web-based information through Internet sites that are commonly used in the context of sexual health.
We searched the Cochrane Database of Systematic Reviews and the Database of Abstracts of Reviews of Effects for systematic reviews published in the past 10 years (from 1996 onwards). Terms used to identify reviews in the Cochrane Database of Systematic Reviews, and those that were successful in identifying relevant reviews were used subsequently to search the Database of Abstracts of Reviews of Effects: (MESH terms) “sexual behaviour†, “contraception†; (free text terms) “sex†*, “sex* near behavio*†, “sex* near risk*†, “sex* near safe*†, “behavio*†, “barrier*†. We included reviews that reported sexual behaviour outcomes or outcomes that are closely associated with sexual behaviour, for example, sexual partnerships (eg, reductions in partner numbers, monogamy, exclusivity), sexual practices (eg, abstinence, condom use, non-penetrative sex), or changes in behavioural determinants associated with either of these (eg, empowerment, self-efficacy, resistance to peer pressure, alternative income generation for commercial sex workers). The results of the reviews were summarised by population group, with emphasis given to reviews done most recently and those providing useful information regarding the essential components of successful interventions.
Analysis of sexual behaviour data
Almost all estimates presented in this paper are made on the basis of original analysis of available survey data.8,14—18 We sought datasets from nationally representative population-based surveys undertaken since the mid-1990s. Table 1 shows the number of countries for which data are available and estimates were obtained. The main sources of data were surveys by the MEASURE DHS (Demographic and Health Surveys) project.8 We have also used data from national surveys from Australia,14 the UK,15 France,16 USA,17 and from an EU-sponsored series of surveys in western Europe.18 We have used published estimates from Reproductive Health Surveys,19—23 from a national survey from Chile24 and from surveys from China25 and the USA.25, 26
More surveys, and more standard measures, were available for African countries than for any other region.8 Data for developed and middle-income countries were the most difficult to obtain because these surveys are not standardised and are done by many different groups, with no standard archiving procedures. Data were analysed with Stata version 9.2. Data from surveys of ever-married women were weighted to produce estimates of age at marriage for all women. Throughout the paper, when we refer to marriage, we include all cohabiting relationships, irrespective of legal marital status.
The choice of indicators was guided by the need to describe key aspects of sexual behaviour relevant to reproductive and sexual health. We report median age at first intercourse and at first marriage. We describe trends in first sexual intercourse using the percentage of the population who first had sexual intercourse before age 15 years. This measure has advantages compared with median age at first intercourse (the age by which half have had sex) since it can be calculated for a younger cohort. We also calculate the proportion of the total population who had intercourse before marriage or cohabitation. We examine entry into marriage using lifetable methods, and describe progression from first sex to marriage in terms of the person-years of life spent in the different states (never had sex, had sex and not yet married).
Patterns of sexual partnerships are described by combining data from two sources. First, using sexual behaviour data, we calculated the proportion who, in the year before the survey, had no partner, one partner, and more than one partner, by age group for men and women. Second, we used 2005 population-estimates from the UN Population Division database27 for all countries to derive population pyramids onto which the patterns of partnership formation were superimposed. We report sexual activity in the previous 4 weeks, by marital status. Our one measure of safer sex, the proportion of sexually active men and women who used a condom on the most recent occasion of sex, is presented for at least two time points.
Accuracy of sexual behaviour estimates
All survey data based on self reports are susceptible to error. Sexual behaviour surveys might suffer more than others in this respect, since they are especially prone to a social desirability bias—the tendency for participants to respond accordiing to social expectations of what is right. Many surveys find that the number of partners reported by men greatly exceeds that reported by women. This difference could be because: women under-report or men over-report, or both; men are having sex with women in age-groups or geographical areas not included in the survey sample, or both; or that with women with large numbers of partners, such as sex workers, are under-represented in the sample.7, 28, 29
Few opportunities exist to assess internal or external consistency of the data. The broad scope of the DHS restricts the number of questions asked about sexual behaviour and hence the scope for assessment of the internal consistency of responses. Similarly, since most countries have only one source of data, few opportunities exist for triangulation between surveys. The quality of the data obtained can, however, be enhanced by use of well designed questionnaires and well trained interviewers. Most of the data used in this paper come from large surveys done by experienced teams. Many of the surveys (most of the DHS and some of the European surveys) used questionnaires based on a common protocol, which increases the comparability of results. Most data come from face-to-face interviews, apart from those in high-income countries, for which telephone interviews and computer-assisted self-interviewing techniques have sometimes been used.
Changes in social attitudes affect the comparability of results between surveys, since what is being captured might indicate increased ease of reporting as well as a change in the behaviour itself. When we describe trends in age at first sex and first marriage by comparison of the experiences of groups born at different times, we have, where possible, pooled the data from two (or more) surveys. By pooling data the sample size is increased, which diminishes sampling error and reduces reporting bias between two surveys; trends in more recent behaviours are harder to determine. Wording of questions has in some cases changed between surveys so that, for some indicators, data from earlier surveys are not strictly comparable with those from surveys done more recently.3, 30
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Table 1<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/table?tableid=tbl1&tableidtype=table_id&sectionType=green>Table image<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/table?tableid=tbl1&tableidtype=table_id&sectionType=green>
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Availability of survey data
Almost everywhere, sexual activity begins for most men and women in the later teenage years (ages 15—19 years), but regional and sex variations between men and women are substantial (table 2). For women, median age at first intercourse is low in regions in which early marriage is the norm (for example, in south Asia, central, west, and east Africa), and high in Latin America and in some countries of the middle east and southeast Asia. For men, age at first intercourse is, in general, not linked to age at marriage. In most African and Asian countries, men start to have sex later than do women. Gender differences are most pronounced in the less industrialised countries.
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Table 2<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/table?tableid=tbl2&tableidtype=table_id&sectionType=green>Table image<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/table?tableid=tbl2&tableidtype=table_id&sectionType=green>
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Age at first sexual intercourse and marriage, for men and women born between 1965 and 1969, by country
None of these data suggest a universal trend towards sex at a young age. The trends are complex and vary greatly with male or female sex. The proportion of women who report early intercourse (before age 15 years) decreased significantly or remained stable between the late 1970s and the late 1990s in four of five countries for which comparisons can be made (figure 1). For men, the proportion either remained stable or increased during that period. The increase was significant in several Latin American and African countries. In societies in which first intercourse still occurs mainly within marriage, the trend towards later marriage has been accompanied by a trend towards later sex in young women,37 and is particularly a feature of countries in Africa and south Asia (figure 2). In some industrialised countries, sexual activity before age 15 years has become more common in recent decades (though the prevalence is lower than in other regions and the increase is not generally significant).
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Figure 1 <http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/images?imageId=gr1&sectionType=green>Full-size image (109K)
Percentage who had sex before age 15 years: comparison between two time points
Difference between groups: *p<0·05, †p≥0·5, ‡Test not possibsible. §Age at first marriage used as a proxy for age at first sex. ¶Ever-married sample and age at first marriage used as a proxy for age at first sex.
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Sexual experience and relationships between ages 10 and 25 years, by successive age-groups in selected countries
Vertical axes show person-years of age, and horizontal axes show people who reached the age of 25 years in years shown. *Data not available for women. †Data not avaiilable for men.
The trend towards later marriage in many countries has also led to an increase in the prevalence of premarital sexual intercourse.38 Again, large regional and sex differences in prevalence exist (figure 3). As shown in figure 4, on average, the time between first sexual intercourse and living with a partner is longer for men than for women (typically 3—6 years compared with 0—2 years,rs, respectively) apart from in industrialised countries, in which the time is about the same for both (about 5 years). Trends in the average time spent between first sexual experience and settling with a marital or cohabiting partner result from changes in both the proportion who have first sexual intercourse before marriage, and the changing interval between these two events. Although the number of countries in which first sexual intercourse and marriage coincide is diminishing39 a clear increase in the intervening period is taking place in only very few countries, again, notably in the more industrialised (figure 2).
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Figure 3 <http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/images?imageId=gr3&sectionType=green>Full-size image (117K)
Percentage of ever-married men and women born in 1965—69 who had sex before marriage
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Figure 4 <http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/images?imageId=gr4&sectionType=green>Full-size image (129K)
Sexual experience and cohabitation between ages 10 and 25 years for people who reached the age of 25 years in 1995—99
Most people are married and married people have the most sex (figure 5). Sexual activity in single people tends to be sporadic and, in most regions, many fewer than half unmarried non-virgins report having had sex in the past month. Single men and women in many African countries are fairly sexually inactive, with two-thirds reporting recent sexual activity compared with three-quarters of those in industrialised countries.
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Percentage of 15—24 year ollds who had sex in the 4 weeks preceding survey, by marital status
CAR=Central African Republic. Denominator for single people excludes those who have never had sex. Single refers to people who have never married. Married refers to people currently married. *Only ever-married women surveyed. †Resppondents aged 16—24 years. ‡Respondents aged 18—18—24 years.
Much is made of the effect on sexual health of the growing prevalence of sex outside marriage; yet marriage does not reliably safeguard sexual-health status. In Uganda, married women constitute the population group in whom HIV transmission is increasing most rapidly. A study in Kenya and Zambia showed that the sexual-health benefits of marriage for women were offset by higher frequency of intercourse, lower rates of condom use, and their husbands' risk behaviour.40 Married women find negotiation of safer sex more difficult than do single women41, 42 and few married women use condoms for family planning.43 Nor can marriage be relied on to ensure safer early sexual experience. In Asian countries where early marriage is encouraged to protect young women's honour, early sexual experiences can be coercive and traumatic and, with respect to early pregnancy, dangerous for mother and child.44
Monogamy is the dominant pattern in most regions of the world (figure 6). Despite substantial regional variation in the prevalence of multiple partnerships, which is generally higher in industrialised countries, most people report having only one recent sexual partner. The data show pronounced asymmetry between men and women (figure 6). Worldwide, men report more multiple partnerships than do women; only in some industrialised countries are the proportions of men and women who report multiple partnerships more-or-less equal. Reporting bias45 doubtless accounts for some of the difference between the sexes. However, in Africa, where young people vastly outnumber older people (figure 6), the difference between men and women can be largely explained by the age structure and patterns of age mixing (ie, older men having sex with younger women). In African countries, in the younger age-groups (those aged 15—19 years), sexual activity is higher in women; more mmen than women report having had no partner in the past year. In older age-groups (those aged ≥20 years), the reverse is true; women are predominantly monogamous, but large proportions of men report having more than one sexual partner. The partners of these men are likely to be the monogamous women from the younger age-group. Median age differences between spouses in Africa are high; 9·2 years in west Africa, 7·4 years in north and central Africa, and 5·5 years in east and southern Africa (age of non-spousal partners is not recorded) (table 3).
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Population distribution by age and sex and number of sexual partners in the past year
These charts present results obtained by applying survey-based proportions to UN population estimates for the year 2005.27 Population numbers are shown in thousands, or in millions, depending on the country.
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Age difference between married men and women, by country
By contrast, in South America (especially in Brazil) more men than women report having one or more recent sexual partners in all age-groups. These findings beg the question of who the men are having sex with. With a median age difference between partners of 4 years, patterns of age mixing and age structure do not account for the difference, and less than 1% of Brazilian men reported sex workers amongst their past three partners. The Latin macho culture might encourage men to over-report, and women to under-report, sexual activity.
These data do not capture whether partnerships exist concurrently or serially. Concurrent sexual partnerships (those that overlap in time) allow more rapid spread of sexually transmitted infections than do the same rate of new sequential partnerships. Evidence is available that, although lifetime numbers of partners might be lower, concurrent relationships in men in some African countries might have been more common and of longer duration than in other regions.46—50 Many men who have sex with men have also had sex with women51 and, apart from in developed countries, are unlikely to identify as being homosexual52 The socially censored nature of same-sex activity could lead to under-reporting and might also account for the absence of such activity from the research agenda. A recent review of the prevalence of same-sex activity in men identified 67 studies,53 none of which were from Africa, the middle east, or the English-speaking Caribbean. Estimates of lifetime prevalence of sexual intercourse with men ranged from 3—5% of men in east Asia, 6 ”12% in south and southeast Asia, 6—15% for eastern Euroope, 6—20% for Latin America.53 The prevalence is 6% in the UK15 and 5% in France.54 About half those with lifetime homosexual experience report having had male partners in the past year.53
The proportion of sexually active young people who report using a condom for their most recent sexual intercourse is higher for men than for women (figure 7). Much of this difference is because young women's partners are more likely to be their husbands, with whom condoms are less often used.48, 55 In most countries for which two estimates are available, condom use at last sexual intercourse is increasing—in some cases, for example in Uganda, strrikingly so. Use of condoms to prevent pregnancy increased from 5% to 19% of single women in 19 African countries between 1993 and 2001, and use of a condom at last intercourse increased from 19% to 28% during the same period.43 In industrialised countries, rates of condom use are generally higher than those in non-industrialised countries, especially in women. The increase in condom use in recent years has also been substantial in industrialised countries. No comparative data are available for the consistency with which condoms are used.
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Percentage of 15—24 year-ollds who reported condom use at last sex in successive surveys
*18—24 year-olds. †â€ 15—19 year-olds only; comparable data are available for 15 ”24 year-old men and women only for 2002: 58% for men, 44% for women. Data shown are for respondents who reported being sexually active in past year.
In countries with wide differences between men and women in the prevalence of premarital sexual intercourse, young men are more likely to report having intercourse with sex workers.44 Estimates of the proportion of men who are clients of sex workers range from 1% to 14% dependent on region.30 Varying operational definitions of sex work frustrate efforts to interpret prevalence at different times and in different places. The continuum of sexual exchange ranges from expectation of gifts or favours within personal relationships, to more formal trading of sex for money.56 The proportion who reported having “sex in exchange for money, gifts, or favours†30 in the past year is highest in countries in central and southern Africa (medians 13·6% and 11·3%, respectively), followed by eastern and west Africa (9·8% and 8·9%, respectively).30 More recent African surveys that used the more restricted definition of paying for sex30 have reported reduced prevalence. In the Caribbean, 6—7% of men reported having paid for sex, and estimatees for Latin America, eastern and western Europe, and central Asia were less than 3%. Cautious estimates are available for northern Africa and the middle east (1—3%), south Asia (3—5%),%), southeast Asia (3—10%), and China and Hong Kong (11%).<30
Estimates from the WHO study on gender-based violence of lifetime prevalence of sexual violence by an intimate partner range between 10% and 50%.57 DHS data lend support to this finding; between 11% and 49% of women say they cannot always refuse sex. In more than half the WHO settings, more than 30% of women who reported first sexual intercourse before age 15 years described having been forced into it, and three-quarters of women who had been abused since the age of 15 years identified the perpetrator as their intimate partner.


Explanations for the variation

The regional variation in sexual behaviour underlines the powerful role of environmental factors in shaping behaviour and its consequences for sexual health. Through the interplay between demographic and structural factors, social norms, and public policies, spatial differences can be properly understood. One of the most notable features of the data, for example, is the striking gender difference in sexual behaviour. Women might be disadvantaged in protecting their sexual health if their partner is older than them, of higher status than them,58, 59 or if they are beholden to a man for favours, goods, or money in return for sex.60, 61 Women's power to maintain monogamous relationships might be diminished in locations in which they outnumber men with whom they might have sex. Women might outnumber men in this way as a result of the age structures of populations and patterns of age mixing, or where cultural practices such as polygyny are prevalent10, 62, 63 and where high levels of imprisonment of black men distort sex ratios in predominantly African-American communities—as in the USA for example.64
Poverty, deprivation, and unemployment work with gender relations to promote change of partner, concurrency, and unprotected sex.64, 65 Economic adversity restricts the power of men and women to take control of their health;66 deprivation and unemployment might drive men and women to sell sex10, 12, 67, 68 or travel greater distances to work. Being away from home is associated in both developed and developing countries with concurrency of partnerships69 and an increase in risk behaviours.46,70—73 Possibly the most powerful influennces on human sexuality are the social norms that govern its expression. Morals, taboos, laws, and religious beliefs used by societies worldwide circumscribe and radically determine the sexual behaviour of their citizens. The scale of the regional diversity in sexual behaviour is matched only by the range of cultural constraints on practice. In some societies, for example, homosexual behaviour is celebrated in public parades of pride; in others it carries the death penalty. In some countries, such as Brazil, condoms are available to young people in schools; in others, for example in parts of Indonesia, their possession is a criminal offence.12 Such strictures hinder attempts by men and women to protect their sexual health. The sexual double standard, whereby restraint is expected of women, whereas excesses are tolerated for men, compounds the problems for both men and women.44,74—77


Interventions to improve sexual health

With the diversity of sexual behaviour, a range of preventive strategies are needed to protect sexual health. And in view of the importance of the broader determinants on sexual behaviour, approaches focusing exclusively on expectations of individual behaviour change are unlikely to produce substantial improvements in sexual-health status. They are especially inappropriate to poor country circumstances, where sex is more likely to be tied to livelihoods, duty, and survival,78 and where individual agency is restricted. In wealthier countries, personal choice is greater than in poorer countries, yet power inequalities persist.79 Numerous calls have been made for public-health interventions to pay greater heed to the social context within which sexual intercourse occurs.78,80—83 Interventions encouraging adoption of risk reduction practices remain a cornerstone of sexual-health promotion but the evidence shows that they need to go beyond mere provision of information to be effective (table 4). Systematic reviews have focused mainly on assessment of interventions to change individual behaviour and show increased effectiveness where information is supplemented by skill building and counselling, such as use of condoms and safe sex negotiation86, 91, 93, 96, 97 where theory guides design,92, 94 where several delivery methods are used,85, 96, 97 and where context and the need for sustainability are taken into account.94—97
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Summary table for effectiveness of interventions
Individual-based interventions also need to be targeted to be successful.88 Men have been successfully targeted in occupational contexts with consequent reduction in sexual-risk taking.87 Young people are most commonly targeted in schools and the evidence is that curriculum-based sex education does not increase risky sexual behaviour as many fear.98 Systematic reviews have shown school-based sex education to lead to improved awareness of risk and knowledge of risk reduction strategies, increased self-effectiveness and intention to adopt safer sex behaviours,98 and to delay, rather than hasten, the onset of sexual activity. Broad-spectrum strategies to achieve behaviour change, with mass-media communication, have proved effective in increasing awareness and knowledge, and in reducing high-risk behaviour.100 In this context, techniques used in social marketing, which target individuals according to their lifestyles, values, and risk status are an improvement on conventional targeting approaches with demographic characteristics alone.101—103
Tailoring of behaviour-change interventions to individual needs and circumstances is also essential. A range of messages is needed that respect diversity and preserve choice. Enough studies have shown that first intercourse is retrospectively regretted by many women, and some men,104 for efforts to help young people to achieve the best timing of first sex to be justified. Yet, abstinence might not be an option where first sexual relations are forced,31, 44 where the sexual abuse of adolescents is common,105 and where financial circumstances force young people to sell sex. Moreover, people do not adhere to only one type of sexual behaviour. Many men who have sex with men also have sex with women, and different preventive strategies might be used for these two behaviours.106 Broader sexual repertoires need to be taken into account. The issue of recommending non-penetrative sex (such as mutual masturbation) is seldom tackled.107, 108 Risk reduction messages need to take account of the diverse reasons for having sexual intercourse109 and for changing sexual behaviour.
Reviews of individual-based interventions also emphasise the importance of interventions to address social norms that act against safer sex.88, 89, 91 The effects of behaviour change interventions will be transient if participants return to an unsupportive environment. Actions such as deferring or denying sex are not intrinsically rewarding and need to be supported by group norms. Community interventions have been effective in mobilising local groups in support of preventive strategies. The prompt response from homosexual communities to the prevention of HIV/AIDS in industrialised countries in the early 1980s owed much to the pre-existence of non-governmental organisation (NGO) infrastructures and to the visibility and mobilisation of homosexual men. The evidence is that information gained through social networks is more salient, and more likely to lead to behaviour change, than that conveyed by more impersonal agencies.110
Where population groups are marginalised and NGOs and community-based service programmes are weak, the starting point might be the informal groups in which norms are maintained. Preventive programmes that use naturally occurring social networks have reduced risky behaviour in homosexual men in Russia,111 increased contraceptive use in married women in Bangladesh,112 increased condom use in sex workers in India,113 and have proved more effective in changing norms than more orthodox approaches using conventional health care and field workers. Strong social prohibitions and sanctions, especially those underpinned by legislation, might present greater challenges. In general, laws protect the young and those vulnerable to coercion and exploitation, but they might also impede safer sex practices. If practices are illegal, they are more likely to be engaged in a furtive or clandestine manner, and opportunities for protection are constrained. The success of preventive strategies is heavily dependent on acceptance of the reality of sexual practices that are socially censured. Condom use is uncommon in sex workers in India113, 114 for example, where commercial sex is heavily socially proscribed. By contrast, condom use is near-universal in those in Kampala115 and in Mexico,116 where public-health agencies have actively and openly engaged in co-operation with female sex workers. The mass media have been powerful in shifting social norms and, in some instances, achieving legislative reform. In the Lebanon, where homosexuality is illegal, a popular weekly television programme includes a homosexual voice.117 In South Africa, the strategic use of entertainment as education, media advocacy, and social mobilisation to change public opinion and influence decision-makers has led to implementation of the Domestic Violence Act.118
To address the broader structural determinants of sexual behaviour is daunting. To do so demands a broader definition of public health than many might feel comfortable working within. Social determinants are the least amenable to intervention. Structural factors such as poverty, unemployment, and gender are difficult to modify, and social and political norms are slow to shift.63, 81, 83, 119 Yet, efforts are being made to address forces such as gender and poverty in innovative ways. These efforts include mainstreaming of HIV and sexual health services in development; empowerment of sex workers to avoid sex work through business and information-technology training; and integration of sexual-health education into microfinance schemes.120 Success has also been achieved in tackling of social attitudes, for example, those of young men towards fatherhood, relationships, and contraception.121, 122
Addressing of structural determinants, particularly poverty, demands the involvement of social as well as health sectors, and so requires co-ordination and collaboration across sectors and agencies, and with other social interventions. The range of people to be engaged in partnership is broad and includes economists, politicians, industry, the judiciary, and NGOs. A way of ensuring that joint action takes place is to make it not merely a generalised goal of interventions, but an explicit component of the programme (as in the case of the UK Teenage Pregnancy Strategy123). Intervention at a structural level needs political will and commitment,124 not least to dismantle legal and other obstacles to pursue strategies to protect sexual health. The successes of Thailand and Uganda in reducing HIV rates show the importance of political leadership (Panel 3, Panel 4).
Panel 3
100% condom-use programme in Thailand
The 100% condom-use programme in Thailand, implemented nationally in 1991, has been widely recognised and documented as an impressive success in achievement of behaviour change. The programme aimed to bring about 100% condom use in commercial sex. Brothel owners, brothel-based sex workers, and their clients were targeted with simultaneous National AIDS Education and Condom Promotion Campaigns125 that used the mass media and workplace programmes. Condoms were made freely available at all sex establishments.
The programme was linked to a longstanding government venereal-disease programme in each province. Sex workers receive regular physical check-ups for sexually transmitted infections, and free condoms. Men who presented with a sexually transmitted infection were asked to name the sex establishment that was the source of infection as evidence of non-compliance with the policy. Public-health officials encouraged sex workers to be tested and treated, venereal-disease units provided extensive contact tracing, and law-enforcement authorities took any necessary legal action against brothel owners.125 Co-ordination between national and local government, public-health officials, and brothel owners was a strong characteristic of the programme. Although prostitution is illegal in Thailand, there has long been tacit cultural acceptance of patronage of sex workers. No attempt was made to eliminate commercial sex or change public morality. With a high level of political commitment and no fear of religious sensitivities, a pragmatic approach to condom promotion was possible.
The success of the campaign was evidenced by an increase in condom use and a decrease in commercial sex and rates of sexually transmitted infection in sex workers and their clients.125 The most convincing evidence is the rate of new HIV infections in 21-year-old conscripts in northern Thailand, which fell from 3·3 per 100 person-years to 0·3 per 100 person-years between 1991 and 1995.124 Condom use in these men rose from 61·0% to 92·5% in the same period.126 The proportion of indirect sex workers (those working from bars, restaurants, etc) increased from half to almost two-thirds, in the first half of the 1990s.124 Although the focus was on making sexual intercourse with sex workers safer, a substantial reduction took place in both supply and demand for sex work. Fear of AIDS might have stopped women entering the trade, and more women started working as indirect sex workers charging higher rates.127 Casual sex with both men and women with low levels of protection increased.126 The proportion of northern Thai army conscripts who report visits to sex workers fell, and decreased even more sharply in older men126 from 81% in 1991 to 64% in 1995. The success of the Thai programme is attributable to efforts made on several fronts. Strategies limited to voluntary individual behaviour change would have been unlikely to achieve such radical change without sociostructural changes.
Panel 4
HIV in Uganda
Uganda's success in reducing HIV prevalence115, 128 and improving reproductive-health status129 compared with neighbouring countries has been attributed to the selective emphasis on the abstinence and being faithful strands of the ABC strategy in the country's HIV programmes.34 The suggestion has been made that later onset of sexual activity and a reduction in non-regular sexual partners (a 65% reduction from 1991 to 1998) have been more important than condom use in curbing the HIV epidemic.130 These conclusions have been interpreted as providing evidence of the merit of abstinence-based approaches to HIV prevention generally.130, 131
Several features of Uganda's epidemiological situation and social-context suggest that Uganda's success should not be attributed to a few specific interventions. The first feature relates to the timing of events. The fall in prevalence of HIV corresponds to a drop in incidence from the beginning of 1985, when Uganda did not have public national HIV-prevention programmes in place. Furthermore, as our data show, the trend towards older age at first intercourse occurred gradually for women from the 1970s to the present—”ie, before the start of HIV-prevention programmes—for men remaarkably little change in age at first intercourse has taken place in recent decades. However, evidence shows that other changes in behaviour have taken place. Condoms were cautiously and gradually introduced in Uganda132 and were largely unavailable to the general population during the 1980s, but rates of condom use were high in high-risk groups, such as sex workers.115
These behaviour changes have been attributed to successful public education campaigns in Uganda. Public-health agencies gained the confidence of communities by galvanising support from local leaders and the church for the Love Carefully and Zero Grazing messages,133 and only later introduced condom-promotion messages to the programme. Yet awareness of the severity of AIDS, its effect on family and friends,134 and the willingness of those affected to publicly endorse behaviour change also played their part.133 Moreover, many have pointed to the broader factors that have contributed to the reduction in HIV prevalence in Uganda, many of which preceded current HIV-prevention programmes.128 These include successful assimilation of scientific knowledge about modes of transmission,135 re-establishment of community life with restored civil stability at the end of the Ugandan civil war in 1986, which substantially reduced prevalence of sexually transmitted infections,129, 136 and two decades of strong policy support.128
Uganda was the first African nation to establish a national AIDS programme137 and the response to the epidemic went beyond individual-level factors. Factors included concerted and integrated efforts made at community level, including mobilisation of local groups, widespread participation of several NGOs in HIV prevention, collaborative partnerships with religious groups and community activists, ample funding, and openness about the scale of the problem and commitment to tackling it at the highest political level. It is the lessons from this joint approach that are most valuably transferred to other settings.137
The evidence shows that, where improvements in sexual health have been achieved, a combination of factors has contributed to the success. Behaviour change in Thailand and Uganda, for example, has been attributed to an array of preventive policies and strategies, mounted by different agencies, with strong partnerships between the media, government, NGOs, sex workers, people living with HIV/AIDS, and international and local public-health agencies, endorsed at the highest political level. Yet, the polarity of views on abstinence, be faithful, and use condoms (ABC) strategies,131 about which of these three elements has contributed most to reductions in rates of HIV in Uganda or teenage pregnancy in the USA (Panel 4, Panel 5), stems from a search for single-factor explanations to support particular ideological positions. The preoccupation with ABC strategies has the negative effect of distracting attention from the need for broader, integrated programmes in which all components are mutually reinforcing.
Panel 5
Teenage pregnancy rates in the USA
Rates of teenage pregnancy in the USA are high by comparison with those in other industrialised countries, but have fallen by 30% in the past decade, from a peak of 117 per 1000 in 1990, to 82 per 1000 in 2001.138, 139 Some studies have suggested that most of the reduction results from increased uptake of abstinence,140, 141 most from increased use of reliable methods of contraception;142 some from both equally,143 whereas others provide evidence that changes in economic factors are responsible, notably the welfare reforms introduced by the Clinton administration.144
If progress is to be sustained, the role of the two main determinants of reduction in pregnancy—ie, deelay in sexual initiation and improvements in contraceptive use—nneeds to be clearly understood. An early study showed that some 25% of the decline in pregnancy in 15—19 year olds between 1988 and 11995 was attributable to delay in sexual initiation and 75% to improvements in contraceptive use, including a shift towards use of more effective contraceptive methods, and a reduction in the proportion who did not use any method.138 A more recent study of high-school students aged 15—17 years, which took into accounnt contraceptive method mix and failure rates,145 showed that these two factors each accounted for about 50% of the fall in the pregnancy rate between 1991 and 2001 for these younger teens. This study had the advantage of accurately matching the time during which the decline in pregnancy occurred, and took into consideration trends in contraceptive method mix, but was unable to include adolescents aged 18—19 years, and had to assume that failure rates weere unchanged during this period, since the most recent failure rates are for 1995. Results from a new study that used national survey data for 1995 and 2002 show that in all 15—19 year-olds, improvementts in contraceptive method use accounts for 86% of the fall in pregnancy rates between 1995 and 2002, whereas a decrease in the percentage of teens who were sexually active accounts for 14% of the pregnancy rate decline.146 All of this contribution occurs in young adolescents ages 15—17 years.146
No reliable evidence is available that abstinence-only sex education is responsible for changes in sexual behaviour of the extent that would explain the drop in teenage pregnancy. Moreover, several factors are likely to determine adolescents' motivation to prevent pregnancy, and therefore no one approach or change would account for the fall that has occurred so far. To sustain the decline in teenage pregnancy, experts recommend that attention is given to a range of risk factors, such as poverty, absence of opportunity, and need to increase specific skills to use contraceptives effectively and to postpone sexual activity.147
The mix of components in national programmes needs to be tailored to the local context.148 Comparisons of HIV policy in different countries104, 132, 149, 150 show the importance of ensuring that public health approaches are culturally appropriate and timely. In Brazil, for example, the adoption of sex positive approaches and explicit condom promotion has been well managed and has ignited little political controversy.149 In Botswana, by contrast, the premature introduction of condom messages to promote condom use without attention to cultural norms served to undermine public confidence in public-health agencies.132 Attention needs to be given to the feasibility and acceptability of interventions that have worked in one setting before introducing them into another. Too often, locally successful models are scaled up without communication and engagement with wider structures and forces.151 Transferability of interventions is now being tested across areas of India with the roll-out of the Sonagachi project, 152 an acclaimed community-mobilisation strategy that involves the active participation of Calcutta's female brothel-based sex workers. Since most commercial sex in India is street based,113 generalisability of this strategy will be put to the test.
An assessment of interventions that adapt elements of the Sonagachi project and the Thai 100% condom programme (panel 3) to the Dominican context,152 compared the effects of community solidarity with and without changes in government policy and showed them to be greater and more sustained when changes in government policy were included in the model. More intervention studies of this kind are needed to assess the effect, not of a single-component intervention in one setting, but of more than one approach, drawing on components from different models in different combinations and in settings other than those in which they originated.
The adoption of multifaceted interventions with a balanced emphasis on changes to individual behaviour and the social context has implications for what counts as evidence of effectiveness. First, the broader the scope of the intervention, the less well it lends itself to assessment by experimental methods that are widely regarded as essential to prove effect.153, 154 Yet a broad scope is what is needed. Interaction and synergy between components need to be seen as valued goals of behavioural interventions rather than obstacles to experimental research. Controlled trials might be the assessment method of choice for individual-based interventions, but in the case of those that tackle social-contextual factors, more can be learned from country case studies that document the experience of implementation of programmes in specific settings. Second, strategic decisions with respect to sexual-health promotion need to be based on a strong understanding of process.155 The emphasis must be not be only on which approaches work, but also on why and how they do so in particular social contexts.
Third, policy-makers and programme designers might need to abandon their preoccupation with seeing progress towards biomedical endpoints as a measure of success.156 The link between sexual behaviour and rates of HIV and other sexually transmitted diseases and unplanned pregnancy is anyway not always easily drawn. Comparative studies have failed to explain the heterogeneity of HIV transmission in Africa157 and developed countries54, 158 in terms of differences in sexual behaviour, and assessment studies have not always shown a link between behaviour change and health outcomes.159 Where the goals of interventions are predominantly social, a reappraisal of the choice of endpoints is essential. When strong evidence exists of a link between changes in the social context and an improvement in sexual health status, achievements that relate to domestic violence,118 gender empowerment,160 and changes in social norms121 can be seen as valid interim endpoints. Failure to recognise them as such might prevent potentially useful interventions from being scaled up,161 which in turn has implications for the timescale of assessments, the length of which has to take account of the slower process of social change.


Conclusions

This is the first time an attempt has been made to bring together comprehensive survey data for sexual behaviour from around the world. The data show perhaps less change over time than might have been supposed. People who fear a tide of youthful promiscuity might take heart from the fact that trends towards early and premarital sex are neither as pronounced nor as prevalent as is sometimes assumed. Similarly, the apparent absence of an association between regional variations in sexual behaviour and in sexual-health status might also be counterintuitive. In particular, the comparatively high prevalence of multiple partnerships in developed countries, compared with parts of the world with far higher rates of sexually transmitted infections and HIV, such as African countries, might hold some surprises. Only rates of condom use are predictably lower in countries with lower sexual-health status, and this is likely to be attributable to factors relating to access and service provision. The data make a powerful case for an intervention focus on the broader determinants of sexual health, such as poverty and mobility, but especially gender inequality.
The comparative data are important in countering misinformation and quelling fears relating to sexual behaviour. The selection of public-health messages needs to be guided by epidemiological evidence rather than by myths and moral stances. The greatest challenge to sexual-health promotion in almost all countries comes from opposition from conservative forces to harm-reduction strategies. Governments tend to be wary of controversy and, faced with resistance from groups with a strong moral agenda, shy away from supporting interventions other than those with orthodox approaches. Policy-makers and programme planners need strong evidence of beneficial effect to make the case to address stigmatised groups and adopt messages that do not support the dominant ethos of monogamous, procreative, and heterosexual sex. Policy-makers and programme planners need to be able to show that the effect on sexual-health status of providing services to unmarried young women, supplying condoms, decriminalising commercial sex and homosexual activity, and prosecuting people who commit sexual violence is likely to be beneficial rather than detrimental, and that to do otherwise will force stigmatised behaviours underground, leaving the most vulnerable people unprotected. Scientific evidence of effectiveness will counter misconceptions (for example, that sex education encourages promiscuity).
Sexuality is an essential part of human nature and its expression needs to be affirmed rather than denied if public-health messages are to be heeded. As we have seen, men and women have sex for different reasons and in different ways in different settings. This diversity needs to be respected in a range of approaches tailored to whole societies, and to particular groups and individuals within them. Public-health strategies include health promotion, social marketing, media advocacy, legislative activities, and community empowerment. Strategies used should enable people to make their own choices, rather than have them imposed on them. Goals related to the improvement of sexual health need to be linked with development goals, and the lynchpin here is partnership between statutory agencies, between sectors, and between national and local agencies, underpinned by political leadership.
Evidence from behavioural interventions shows that no general approach to sexual-health promotion will work everywhere and no single-component intervention is likely to work anywhere. Comprehensive multilevel, multipartner behavioural interventions are needed that take account of the social context in mounting individual-level programmes, attempt to modify social norms to support uptake and maintenance of behaviour change, and tackle the structural factors that contribute to risky sexual behaviour.
Conflict of interest statement
We declare that we have no conflict of interest.
Acknowledgments
We thank Joanna Busza, John Cleland, Roger Ingham, Shireen Jejeebhoy, Simon Lewin, Cicely Marston, Sandra McDonagh, Justin Parkhurst, Nono Simelela, Lindsey Gilroy, Alfred Spira, James Trussell and Ravi Verma for commenting on earlier drafts of this paper; Ahmet Gulmezoglu and Anna Glasier for guidance with this paper, Lawrence Finer and Suzette Audam for their assistance with data analysis; and the UK Department for International Development for funding ES and MC during the time this paper was written.


References

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<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/fulltext?_eventId=login#back-aff1>a London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/fulltext?_eventId=login#back-aff2>b Guttmacher Institute, New York, NY, USA
<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/fulltext?_eventId=login#back-aff3>c Population Services International, Johannesburg, South Africa
<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/fulltext?_eventId=login#back-aff4>d Institut National de la Santé et de la Recherche Médicale (INSERM), le Kremlin Bicetre, Paris, France
<http://www.thelancet.com/journals/lancet/article/PIIS0140673606694798/fulltext?_eventId=login#back-cor1>
Corresponding Author
 Correspondence to: Professor Kaye Wellings


Thomas R. DeGregori, Ph.D.
Professor of Economics
University of Houston
Department of Economics
204 McElhinney Hall
Houston, Texas 77204-5019
Ph. 001 - 1 - 713 743-3838
Fax 001 - 1 - 713 743-3798
Email trdegreg@uh.edu
Web homepage http://www.uh.edu/~trdegreg